Troubleshooting Color - Printers
In our last newsletter we looked at how to track down the source of color problems on displays. We also looked at some good general advice for what to do now, that can aid you down the road when color problems happen. Some of that advice is good for print problems too, so you can review those tips from last time here.
A profile will last forever if the conditions that existed when it was created continue with no change. If your printing workflow is producing a different color, consider that one of the following has changed:
Different papers will absorb ink differently. A high quality matte art paper may look identical to another matte paper, but the way the coating on the paper absorbs the ink can be completely different. Unless you have established that two different papers will print identically, you should plan on a different profile for each paper type.
The first place to check when you see color problems in an inkjet printer is to print a nozzle check pattern to make sure there are no clogged ink heads. Keep in mind that it is essential that your profiling target was printed correctly too. If it had clogged ink nozzles when printing the target and you did not know about it, no software is going to make a good profile out of that target. You would need to start all over again with a new target to be sure. Has there been any recent change in the ink lately? Check to see if the wrong cartridge is in place (like a light cyan cartridge in the location for a regular cyan). Ink that has been sitting on a shelf (or sitting in your printer) for six months or more may have pigments settling unevenly. Check the expiration dates on the ink. Once in awhile we hear about a bad batch of ink. The color snapped back into place after replacing the old cartridge with a new one, and purging the old ink through the system.
Last time we discussed the need to document your settings. Make sure you’re using the right configuration or environment settings for your RIP. Usually a different resolution or a different setting between high speed/ low speed does not make a big difference in color, but it can make a small difference.
If you are printing through a printer driver, you really want to save a preset for each paper type you print onto. For example, use the “luster-1440” preset you saved every time you print with that paper. It is essential for color consistency that you use the same settings every time.
Are you using the right rendering intent for what you need? Different rendering intents will give a more subtle change in color. For example, the perceptual rendering intent will tend you give you less saturation overall, while the relative colorimetric intent will give you more saturated colors. More on rendering intents is here.
Check to see that you are not applying a printer profile in more than one place. This is a common problem for RGB workflows printed through printer drivers. It is possible to have a profile in place in Photoshop for example, and then also to have the operating system use another profile deep in the bowels of the driver settings. A printer profile must be used in one place or the other, not both.
Has the printer driver version changed? Any time we upgrade to a new version of the driver, there is a possibility that the algorithms behind the media settings have changed. This is true for operating system updates as well if they involve printer drivers. Most of the time your color will stay the same. But if you upgrade to a new driver and your color changes, even though you’re using the same media settings, then that is probably the cause. It is time to get a new profile or revert back to the old driver.
This is a long shot, but sometimes a print head will gradually change the way it prints over time. If you have already verified that your media, ink and settings have not changed - sometimes the only thing left to do is to create a new profile and chalk it up to some mysterious hardware glitch. It drives some people nuts to not know why the color went bad, but if you have to get the work out, then you do what you have to do. Making a new profile will at least fix the color. You will be wise to keep a close eye on things to see if the color changes again though. One unexplained change in color can easily lead to another unexplained change, and you can end up chasing your tail as it were.
If you are working with a traditional or digital press, you have another set of variables to deal with in print variation. It could be beginning of run vs. end of run, cross-sheet variation or a host of hardware-related issues that will affect the consistency of color on the sheet. It’s beyond the scope of this article to walk you through troubleshooting a press, but I will say that it pays to keep this variability in mind. Don’t make decisions based on one or two samples. It’s wise to get an average. Smoothing measurement data will do a lot to curb some of the extreme outlier measurements that don’t truly represent the normal functioning of the press. For example, our Curve3 software has a very good smoothing algorithm that can be called into service to smooth any measurement data. A good press profile will average the measurements from several samples throughout the run. Our Digital PressWatch service in Maxwell helps to visually see where cross-sheet variation is happening.
There are some cases where a single image was used to verify the testing of a profile, so the entire capability of the profile/device was never tested. A similar thing can occur when, for example, a CMYK profile is successfully used for proofing, and months later when the profile is used for separations, a problem shows up. In both of these cases the flaw was always present in the profile, and incomplete testing lead the user to believe it was a good profile when in fact it was not.
It’s always good to consider that maybe your original color was wrong to begin with - and your color now, while “different,” is correct. Maybe you have been running all these years with a generic profile, and now that you have just started making custom profiles, you suspect the color is bad because it is different from what you have gotten used to? Perhaps your original profiling target had some print defect, or something went wrong with the profile building years ago when it was originally done? You may never find out what happened, but if things are looking good now, then go with it.
Is your measurement instrument reliable?
X-Rite makes available a program called i1Diagnostics that will walk an X-Rite instrument through its paces and give a verdict on whether it is good or bad. At the conclusion of this process, you get a rudimentary result as to whether your instrument passed the tests or not. It is sometimes quite useful, but be cautious about putting too much weight on the results. It is especially good to run this test and save the results so that you have something to compare the numbers to if your device actually does go bad someday.
You can get a genuine, quantified judgment on the quality of your measurement device if you compare its measurements to a control tool that was measured at the factory. These come in the form of small control strips that are specially made of long-lasting material and have been pre-measured with a high quality spectrodensitometer. You can compare how your measurement compares to the factory measurement of the exact same strip of colored patches.
Maxwell has a service called MeasureWatch where a control tool is bundled with our Maxwell tracking services to provide an easy way to track the accuracy of a measurement device over time. It is one more way to eliminate another variable when trying to track down the cause of a color problem.
Remember the auto-white balancing feature in our eyes? Lighting conditions can affect how you perceive color, so be aware of your ambient lighting. Unless you have great confidence in your viewing booth, take the print outside and view it in natural daylight on occasions. Printers are profiled so their prints look proper in true daylight. There is a problem called metamerism which is related to this and can be caused by the inks used, or by lighting. Here is an article on Metamerism.
Even the color of the walls in your room will affect how you perceive color in a display or a print that you are viewing. That beautiful western view out your studio provides great inspiration for your design work, but as the sun sets and the room is bathed in a golden glow, the prints off your printer will look more warm, and the images on your display will look increasingly colder by comparison. A neutral visual environment that does not change is preferred. People in the know actually buy paint that is specifically formulated to be perfectly neutral gray.
If your printed image has a white border around it, it will appear significantly darker than if it is cut out of the surrounding white or if it has a black border. The same thing is true for an image on a display. An image with a white background on screen will look a lot darker. When you switched to that newer version of Photoshop or Lightroom with a dark surround, did you notice your images all looked a little lighter? This white border business makes a big difference, and if you have never actually experienced this perception change, you should take a few moments to try this for yourself.
I spent a little time at the end here to present some perceptual problems with color. When something does not look right, it might not always be about hardware or software. The way our brains interpret the signals they get from our eyes can have a bigger effect than most people realize, so it’s good to keep in mind the possibility of an optical illusion of some kind as you track down that elusive cause of your color problem.
Thanks for reading,
CHROMiX Tech Support